Acute central nervous system infections in adults--a retrospective cohort study in the NHS North West region.

BACKGROUND Over the last 15 years, bacterial meningitis has received considerable attention, including national guidelines, whilst viral central nervous system (CNS) infections have been relatively neglected. A recent pilot study suggested that management of patients with suspected viral encephalitis was often suboptimal. AIM To examine the relative incidence, clinical features and management of suspected acute CNS infections in adults across the NHS North West Region. DESIGN A multicentre cross-sectional retrospective cohort study at 10 hospitals across the region over 3 months (from September to December 2007). Following a screen of all patients who had cerebrospinal fluid (CSF) analysis or received intravenous aciclovir and/or third-generation cephalosporin, those with clinical features suspicious of a CNS infection were included. Management was compared with the national meningitis and regional encephalitis guidelines. RESULTS Three hundred and eighty-five patients were screened; 217 patients had a suspected CNS infection and 44 (20%) had a CNS infection: 18 aseptic meningitis (one herpes simplex virus [HSV]-2), 13 purulent meningitis (four Streptococcus pneumoniae) and 13 encephalitis (three HSV-1). The median (range) time from admission to suspicion of CNS infection and to LP was longer for patients with encephalitis than meningitis [4 (0.3-312) vs. 0.3 (0.1-12) h, P<0.001, and 23 (4-360) vs. 12 (2-48) h, P=0.042, respectively]; and the median time to treatment was longer for aciclovir than cephalosporin [7 (0.5-312) vs. 3 (0.3-312) h, P=0.002]. DISCUSSION Encephalitis was as common as purulent meningitis, and HSV as common as Streptococcus pneumoniae. However, the management of patients with encephalitis was worse than meningitis. National encephalitis guidelines are needed.